1. Field of the Invention
The present invention relates generally to aqueous silane compositions and, more particularly, to aqueous silane compositions for use in making absorbent surfaces, such as masonry, water repellent.
2. Description of the Prior Art
Aqueous silane compositions have become important for making absorbent surfaces, such as masonry, water repellent. U.S. Pat. No. 5,965,644 issued to the assignee of the present application, in the names of Lindley, et al. on Oct. 12, 1999 and entitled xe2x80x9cHigh Concentration Silane Emulsions For Rendering Absorbent Substrates Water Repellentxe2x80x9d describes aqueous silane compositions for use in making absorbent surfaces, such as masonry, water repellent. The entire disclosure of U.S. Pat. No. 5,965,644 is hereby incorporated by reference.
However, the known aqueous silane compositions are in some respects in need of improvement. Often, the water concentration required to obtain a stable aqueous silane composition adds significantly to the cost of shipping. When stable low water concentration aqueous silane compositions are obtainable, their shelf life is often unacceptable since the components readily segregate into zones having different water concentrations. These segregated zones in time become layered.
The segregated compositions are not remixed readily into a homogenous aqueous silane composition. Dilutions are often used to adjust a water content of the aqueous silane compositions to levels appropriate for use with absorbent substrates to render them water repellant. Such dilution of inhomogeneous aqueous silane compositions using water additions often do not get rid of the segregation. Thus, segregated aqueous silane compositions are discarded as waste.
Another deficiency of known aqueous silane compositions is the depth of impregnation for example of masonry in the building sector. The deeper an aqueous silane composition penetrates into masonry, the better the water impermeability of treated masonry. In situations involving spatting and chipping, water impermeability is maintained when the depth of penetration exceeds the depth of spalling and chipping. Also, deeper penetration provides better water impermeability in driving rain conditions. However, the depth of penetration for impregnations leaves something to be desired in many current aqueous silane compositions.
The following discussion is generally taken from U.S. Pat. Nos. 4,877,654 and 4,990,377 to Wilson. The entire disclosures of Wilson ""654 and ""377 are hereby incorporated by reference.
The utility of silanes, especially alkoxysilanes, as masonry water repellents is widely known. Compositions currently in use employ solutions of silanes in various organic solvents such as alcohol, e.g., U.S. Pat. Nos. 3,772,065, to Seiler and 4,342,796, to Brown et al. or hydrocarbons, e.g., 4,525,213 to Linn. Principal limitations of such solvent type compositions include the toxicity and the flammability of the solvents employed.
Aqueous silane compositions that are non-toxic and non-flammable have become important as effective masonry water repellent compositions. See, U.S. Pat. Nos. 4,433,013, to Puhringer, 4,517,375 to Schmidt and 4,648,904 to DePasquale and U.S. Pat. Nos. 4,877,654 and 4,990,377 to Wilson. Such compositions can have an important drawback, however, in that the pH may tend to drift and then the silane reacts with water and hydrolyses. See, e.g., U.S. Pat. Nos. 2,683,674 to Hatcher et al. and 4,175,159, to Raleigh. This reduces efficacy by reducing the content of active, water-repellent ingredient. Moreover, the pH of the system may shift when additives are included such as a biocide, which is commonly added to retard growth of fungi and the like.
Although the stability of the water-containing emulsions has been enhanced to some extent by refrigerating them, or the problem of reduced efficacy can be avoided by using the emulsions soon after preparation, both expedients are not cost-effective and may in some cases cause waterproofing contractors to go back to the above-mentioned solvent borne, non-aqueous compositions.
In some cases, the pH of the system has been adjusted to increase the rate of resin formation, see e.g., U.S. Pat. Nos. 4,552,910 to Deubzer et al. and 4,228,054, to Ona et al. Wilson, in U.S. Pat. No. 4,877,654 teaches that by selecting appropriate silanes (largely water insoluble) and appropriate emulsifiers, water-based, normally hydrolysable silane emulsions may be prepared that are hydrolytically stable if the pH is maintained in a predetermined pH stable range, typically 6-8, with a buffering compound such as sodium bicarbonate. However, Wilson only teaches concentrations of less than about 60 percent and, in fact, his preferred compositions are about 40 percent. Significant savings in packaging and shipping could be obtained if the concentration could be increased since most of the current products are water which could easily be re-added at the site where the composition is being applied.
Thus, there remains a need for a new and improved aqueous silane compositions for use in making absorbent surfaces, such as masonry, water repellent which is hydrolytically stable for a long period without necessarily requiring a separate buffering compound while, at the same time, may be prepared in much higher concentrations to reduce packaging and shipping costs.
The present invention is directed to an aqueous silane composition for increasing the resistance to penetration by aqueous media of an absorbent substrate. The composition is made from effective amounts of ingredients including: a hydrolyzable silane; a low molecular weight silicone; an amino-functional silicone; an amino-functional silane; and the balance of water.
An amino functional silane that has been reacted with a non-ionic emulsifier may used in amounts of about 0.5 weight percent of the composition. The non-ionic emulsifier used in the reaction preferably includes one having reactive hydroxyl groups. For example the non-ionic emulsifier may be an ethoxylated alkyl phenol.
Alternatively, a non-ionic emulsifier may be directly added to the composition. In this case, the non-ionic emulsifier may be directly added to the composition and may be between about 2 and 3 percent by weight of the composition.
The hydrolyzable silane is an alkyl-silane, preferably an alkoxy-silane such as octyl-triethoxy-silane, hexadecyl-triethoxy-silane, hexyl-triethoxy-silane and hexyl-trimethoxy-silane.
A combination of the hydrolyzable silane and the low molecular weight silicone may be between about 0 and 90 percent by weight, preferably between about 30 and 90 percent by weight, and more preferably between about 35 and 75 percent by weight, of the composition.
The low molecular weight silicone may be between about 10 and 90 percent by weight of active components of the composition ({Silicone(s) and Silane(s)} e.g., hydrolyzable silane and low molecular weight silicone; or hydrolyzable silane, low molecular weight silicone and amino-functional silicone; or hydrolyzable silane, low molecular weight silicone, amino-functional silicone and amino-functional silane . . . etc. depending on which are present in the composition). Preferably, the low molecular weight silicone may be between about 20 and 80 percent by weight of the active components of the composition. More preferably, the low molecular weight silicone is between about 40 and 65 percent by weight of the active components of the composition.
The low molecular weight silicone may be represented by the formula:
R1xR23xe2x88x92xSiOxe2x80x94[SiR1R2O]nxe2x80x94SiR1xR23xe2x88x92x,
where R1 is any one of H, xe2x80x94(CH2)y(CH3) y=0,1,2, or 3, xe2x80x94CH(CH3)2, and
xe2x80x94(CH2)yCH(CH3)2 y=0,1,2, or 3;
R2 is any one of xe2x80x94O(CH2)xCH3 x=0,1,2, or 3 and
xe2x80x94O(CH2)yCH(CH3)2 y=0,1,2, or 3; and
n is an effective value. Although not fully knowing the range of effective values for n, applicant believes that the range of effective values for n is low, such as, n=0,1,2,3, or 4.
Preferably, the low molecular weight silicone is represented by the formula:
R1xR23xe2x88x92xSiOxe2x80x94[SiR1R2O]nxe2x80x94SiR1xR23xe2x88x92x
where R1 is any one of xe2x80x94(CH2)y(CH3) y=1, 2, or 3, xe2x80x94CH(CH3)2, and
xe2x80x94(CH2)xCH(CH3)2 x=1,2, or 3;
R2 is any one of xe2x80x94OCH2CH3 (ethoxy) and
xe2x80x94O(CH3) (methoxy); and
n is an effective value. Although not fully knowing the range of effective values for n, applicant believes that the range of effective values for n is low, such as, n=0,1,2,3, or 4.
Specific examples of the low molecular weight silicone include: 
The amine value of the amino-functional silicone or siloxane may be in the composition in an amount between about 50 and 100 mg KOH/gm, preferably about 70 mg KOH/gm. The amino-functional siloxane may be about 0.5 percent by weight of the composition.
The present invention also provides a method for increasing the resistance to penetration by aqueous media of an absorbent substrate by applying to the surface of the substrate the composition as above defined and allowing the composition to cure.
Mention is made of embodiments of this invention involving compositions and use of such compositions as defined above including an effective amount of a biocide.
Accordingly, one aspect of the present invention is to provide an aqueous silane composition, the composition initially comprising effective amounts of: a hydrolyzable silane; a low molecular weight silicone; and the balance of water.
Another aspect of the present invention is to provide a low viscosity aqueous silane composition, the composition initially comprising effective amounts of: a hydrolyzable silane; a low molecular weight silicone; an amino-functional silicone; and the balance of water.
Still another aspect of the present invention is to provide an aqueous silane composition for increasing the resistance to penetration by aqueous media of an absorbent substrate, the composition initially comprising effective amounts of: a hydrolyzable silane; a low molecular weight silicone; an amino-functional silicone; an amino-functional silane; and the balance of water.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.